Time and the river; life in ancient Egypt was geared to the annual Nile flood
Without the Nile, which flows north from the Ethiopian highlands and Central Africa to the Mediterranean, Egypt with its negligible rainfall would have been almost completely inhospitable. Because of the river, it was the largest and most prosperous East Mediterranean State from 3000 BC until the Roman conquest in 30 BC.
Baines, John. "Time and the river; life in ancient Egypt was geared to the annual Nile flood." UNESCO Courier, Sept. 1988, p. 4+. Academic OneFile, https://link.gale.com/apps/doc/A6841316/GPS?u=maine&sid=GPS&xid=50dfa0f5.